1. Field of the Invention
The present invention relates to a switch device having a coil antenna for emitting a radio wave for energizing an external portable device.
2. Description of the Related Art
In recent years, there has been used in the art a smart ignition system for making the engine on a vehicle ready to start when the driver of the vehicle presses the control button of an engine starter switch (switch device) of the vehicle providing that a portable device carried by the driver and the vehicle have their ID information agreeing with each other upon communication with each other.
Usually, such a switch device has a coil antenna for performing wireless power feeding on the portable device. If the portable device fails to check the ID information against the vehicle due to a cell power failure, then the coil antenna induces an electromotive force in a transponder of the portable device that is held in the vicinity of the control button.
For example, Japanese Laid-Open Patent Publication No. 2011-060626 discloses a switch device having a coil antenna which is disposed inside or behind a control button and whose outside diameter is smaller than the inside diameter of the control button.